1. Field of the Invention
The present invention relates to concrete products and more particularly to an admixture formulated to control efflorescence in concrete products, particularly dry-cast concrete products.
2. Description of the Related Art
Efflorescence can be a significant problem in concrete products particularly dry-cast concrete products exposed to moisture in service. Efflorescence is the deposit of salts on the surface of concrete. The salts are leached out of the concrete with water and crystallize on subsequent evaporation of the water.
There are two types of efflorescence, primary (early, short-term) efflorescence and secondary efflorescence. Primary efflorescence is the result of salts which leach out from the cementitious mix upon evaporation of mix water. Secondary efflorescence is the result of salts which leach out of the concrete with water which moves through the concrete substrate, either continuously or intermittently, or with water which comes from exposure of the concrete surface to alternate wetting and drying.
There are admixtures available which are directed toward minimizing efflorescence, but most of these are only effective in controlling either primary or secondary efflorescence. There is still a need for a product which will minimize both primary and secondary efflorescence in concrete products, particularly dry-cast concrete products, without significantly compromising performance criteria, e.g. compressive and flexural strength.